In integrated circuit (IC) devices, resistive random access memory (RRAM) is an emerging technology for next generation non-volatile memory devices. RRAM is a memory structure including an array of RRAM cells each of which stores one or more bits of data using resistance values, rather than electronic charge. Particularly, each RRAM cell includes a resistive material layer, the resistance of which can be adjusted to represent different logic values, e.g., logic “0” or logic “1.” RRAM devices operate under the principle that a dielectric, which is normally insulating, can be made to conduct through a filament or conduction path formed after the application of a sufficiently high voltage. The forming of a filament or conduction path is the forming operation or forming process of the RRAM. The sufficiently high voltage is the ‘form’ voltage. The conduction path formation can arise from different mechanisms, including defect, metal migration, and other mechanisms. Various different dielectric materials may be used in RRAM devices. Once the filament or conduction path is formed, it may be “reset”, i.e. broken, resulting in high resistance or “set”, i.e. re-formed, resulting in lower resistance, by an appropriately applied voltage. There are various architectures to configure an array of RRAM cells. For example, a cross-point architecture includes a RRAM in each cell configured between a crossed word line and bit line. Recently, a transistor type architecture that pairs an RRAM with a transistor (1T1R) in each cell has been proposed that can improve random access time.
For random-access type memories, a 1T1R (one transistor, one resistor) architecture is well-suited because the transistor isolates current to cells that are selected from cells that are not. On the other hand, a cross-point architecture is more compact and may enable vertically stacking memory layers, suited for mass-storage devices. However, in the absence of any transistors, isolation must be provided by a “selector” device, such as a diode, in series with the memory element or by the memory element itself.
Research is being conducted to improve the performance of RRAM before its commercial utilization. There is a need for improving the performance of RRAM.